Bats, diseases, and the Ebola epidemic

in #science4 years ago (edited)

After discussing in length about how wonderful bats are for our agriculture and for our forests, in my last post, I hinted at the fact that they also carry diseases that are sometimes lethal when transmitted to humans.

I specifically mentioned rabies in that post. The website maintained by Centers for Disease Controls and Prevention tells us that contact with bats is the most common way by which people get rabies in the United States. The same article begins by saying “Most bats don’t have rabies.” It also mentions that among bats that are tested for rabies (after suspicious symptoms are observed), only 6% are found to have the virus.

But rabies is not the only one

Commenting on my last post, @mountainwashere mentioned that bats have also been known to be natural reservoirs for Nipah and Hendra viruses. A natural reservoir is an organism which acts as a host for a disease-causing parasite without getting sick itself.

Bats have been found to act as reservoirs for an astonishing array of viruses dangrous for human beings. In a 2006 article focusing on this topic, the authors discuss 66 different viruses isolated from or detected in bats.

These words appear in the abstract of the same article:

“It is clear that we do not know enough about bat biology; we are doing too little in terms of bat conservation; and there remain a multitude of questions regarding the role of bats in disease emergence.”

And the bats are scary again

The authors of that study appear worried about indiscriminate killing of bats fueled by the new discoveries relating bats with emerging viruses. Similarly, the authors of a 2003 article on Brazilian bats express concern about how vaccination against exposed livestock was not being made a priority, but bats were being killed indiscriminately.

In order to have a clearer picture of this process of transmission from bats followed by destruction of bats, let us look at a recent outbreak of a virus that has also been linked to bats.

Then comes Ebola

In December 2013, a mysterious disease started spreading in the West African country of Guinea and it remained mysterious until it was identified in March 2014. It was identified as the Ebola virus which causes fever, headache, fatigue, diarrhea, vomiting, stomach pain, and if left untreated, death. It quickly spread to other countries in Africa and around the world. Finallly, on January 13, 2016, the World Health Organization declared that Liberia, the last of the country affected, was Ebola-free.

In about two years, 11,315 people had died from infections in Guinea, Sierra Leone, Liberia, Nigeria, Mali, and the United States.


The ebola cycle
Image is in the public domain.

Unpredictable outbreaks of Ebola had been reported since 1976, but this was the biggest epidemic of the virus resulting in the largest number of reported cases and deaths. Scientists had been puzzling over the source of this virus for a long time. Many animals, including antelopes, chimpanzees, and gorillas were found to contract the virus and die. Humans could get the virus by touching or eating these dead or infected animals, but the problem was scientists had not been able to find any living organism carrying the virus.

And the answer was bats

Bats are presumptive reservoirs for Ebola because antibodies that fight against the Ebola virus have been detected in bats. This means that some species of bats can survive when infected with the ebola virus. An antibody is a cell used by the body to fight against bacteria or viruses. So if an antibody against a certain virus is found in an animal body, we can assume that the animal has previously been infected by that disease and has survived that attack. That is the principle on which vaccinations work.

A little detour into antibodies

For example, the vaccine for the smallpox virus, which has saved billions of lives, introduces a similar but less dangerous cowpox virus into the body. The body creates antibodies that fight the cowpox disease, and these antibodies will stay in the system and will also fight the smallpox virus. So if we tested an immunized person and found the antibodies against cowpox, we could say that the person had been infected by cowpox and had survived it, and we would be correct.

To be completely accurate, modern versions of the smallpox vaccine use a different virus that is related to both the cowpox virus and the smallpox virus. Edward Jenner, who pioneered the vaccine, used the cowpox virus (or the smallpox of the cow). Because of this, the word “vaccine” is itself derived from the Latin word for cow.

Back to Ebola

In order to determine where the Ebola outbreak started, a group of scientists conducted a retrospective case study. They used “surveys, interviews, and molecular analyses of bat and environmental samples” that led them to a case involving a 2-year old boy in a remote village called Meliandou in Guinea. The boy had got sick and died within a few days followed by his family members followed by the people who went to their funerals and the epidemic had spread across the country and the world. The scientists then tried to figure out how the boy could have contracted the disease.

Their analysis led them to a hollow tree with a roost of bats where the boy had been known to play. The insectivorous free‐tailed bats (Mops condylurus) had previously been found to be resistant to the virus infection and the researchers believed that the boy had come in contact with the bats and thus contracted the disease. When the researchers reached the village to study the bat colony, the tree had been burned and there was only a stump present. The villagers said there had been a rain of bats as the fire engulfed the colony along with the tree.

Some believed that the villagers had burned the tree with the bats inside after learning about the possible connection to the Ebola that had caused them so much suffering.

Bigger reasons

The village of Meliandou is located in what is called the Forest Region of Guinea. A WHO report on the origins of the 2014 Ebola outbreak mentions how that name is ironic because 80% of the forest in the region has been destroyed by foreign mining and timber operations. The same article mentions that this could have caused the wild animals to come into contact with humans leading to the transmission of the virus.

Answers are not final

More recently,researchers found that Ebola was more widespread than suspected, and that several more species along with the bats could be potential carriers of the virus. One of the researchers quoted in that article says, “We don’t want people to be alarmed that there are so many different species, and start killing as many as possible.”

Conclusion

As always, the picture is quite complex. Bats do carry harmful viruses, but we certainly do not want to destroy them. That would leave us with unpleasant consequences in our agriculture and forests and insect populations. So the best way out is to learn the art of peaceful coexistence, and to help conserve their natural habitat.

Having said that, please get medical attention if you are bitten by a bat. This page has information on what to do in case you (or your pet) come in contact with one.

Links to references and image sources are provided in the text.

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Very nice post! Thank you. steemstem rocks, doesn't it?!? Upvoted!

Great post!

I didn't know bats were such a reservoir for diseases. In my non expert opinion, killing them is thus of course not the solution, but studying them is instead (to learn how to get vaccines and possible medication).

Also in my non expert opinion, I agree with you. If we could learn how bats manage to be immune to all those viruses, it would certainly tell us a thing or two about making our vaccines and medication. Thanks for reading and for the comment. :)

Yep. At the end of the day, it may be a matter of fundings to undertake the studies. As for many things.

Great post, and thanks for the mention!

For anyone interested in this topic, I highly recommend David Quammen's excellent book Spillover, which is all about zootics, diseases that spread between humans and animals. (Lots of stuff on bats in there!)

I will have to look at that book. Thank you!

Hi @zycr22, I was planning on writing a blog post about vaccines that covers a few aspects of the science surrounding them (antibodies, initial creation, how they work, debunking myths, etc) and as a part of my research I wanted to include other sources from fellow steemians, scientific articles, journals, etc. I was wondering if you would be okay if I referenced this post as part of the research. I know it may come out after this post has paid out... If you do not want me to reference you then that is fine.



Your post was very well written by the way! I used to live out in the country and it was common to see bats swooping when we had a fire and often when looking in the bat houses we could see them. Thank you for sharing, the post was good is what I mean to say.

Hello there @kryzsec. Thanks for reading! :)

Please go ahead and reference this if it will help your post, and don't worry about when you do it. I am glad you are writing about this topic because there are quite a few anti-vaccination ideas being passed around here. I look forward to reading it.

Había visto tu post pero no había entrado porque estaba algo ocupado con mi trabajo. Una vez más, nos traes una información interesante. Para esta ocasión los datos sobre la vacuna son relevantes. Cuando leo este tipo de post, recuerdo la película el contagio. Si no la has visto te la recomiendo. Saludos y feliz día.

If a person gets rabies does that person really go bat shit crazy?

I just learned that "bat-shit" was only a variant of "bull-shit" until the early 1980s. People aren't sure why it started meaning "crazy." Possible reasons are that "bat shit", which is called guana, apparently causes health problems too, AND was once used to extract an ingredient used in gunpowder. I know I get carried away. Thanks for reading.

Congratulations @zycr22, this post is the second most rewarded post (based on pending payouts) in the last 12 hours written by a User account holder (accounts that hold between 0.1 and 1.0 Mega Vests). The total number of posts by User account holders during this period was 2452 and the total pending payments to posts in this category was $2419.28. To see the full list of highest paid posts across all accounts categories, click here.

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Bats has always been my arch enemy from a toddler, even when i never knew they make fantastic hosts to dangerous diseases.

Nice job mate, will chat you up on chat.

Thanks for reading. See you around!

Very welcome dear friend.

Definitely worth an upvote and a resteem :)

Thank you!

nice my friend pliss vote and follow me

hi,zycr22,nice to read about you.
am jeevansantoshi from india,am also new on steemit and welcome you to steemit.
i have followed you.So,can also follow me.
Best of luck!